This invention relates to apparatus for the administration of anesthesia, and more particularly to safety apparatus for facilitating removal of anesthetic gases safely from the operating area.
A conventional method for administration of gaseous anesthesia features the so-called patient anesthesia circle, wherein oxygen and the anesthetic gases are coupled to the patient for inhalation, and exhaled gases are passed through a carbon dioxide absorber and back to the entry point of oxygen and anesthesia. One way valves isolate the patient from the source of anesthesia and the carbon dioxide absorber, and a reservoir bag is provided on the patient's side of the valves. In such a system, it is important to provide apparatus in the circle to prevent pressure build ups which may be harmful or fatal to the patient. To this end, pressure relief valves conventionally are included, which are designed to open the system to the atmosphere when pressure exceeds a predetermined threshold. The most common designs of such valves feature diaphragms or pistons which are held in place by the force of a spring. When pressure in the circle is sufficient to deflect the spring, the diaphragms or pistons are displaced, and pressure is relieved.
In a co-pending application of John R. Boehringer, Ser. No. 609,072 filed Aug. 29, 1975 and entitled "Pressure Relief Valve for Anesthetic Administration," there is disclosed a type of valving apparatus which provides safe and reliable pressure relief for the patient circle, and which also is amenable to systems wherein anesthesia gases expelled from the patient circle are safely removed from the operating area, such as by means of vacuum pumps. That development reflects the attention recently given to the fact that operating room personnel often are undesirably exposed to anesthetic gases which are permitted randomly to enter the ambient atmosphere. Vacuum exhaust systems, also known as scavenging systems, have been devised for removal of the gases prior to their introduction in the operating room atmosphere.
Although the vacuum systems currently developed do an adequate job of removing the anesthetic gases from the patient circle, they also have tended undesirably to endanger the patient. That is, unless safety interface apparatus is provided intermediate the vacuum pump and the anesthetic circle pressure relief valve, there exists the possibility that a vacuum will be applied directly to the patient's lungs during malfunction or misuse of the various anesthesia administration devices.
It is a primary object of the present invention to provide safety interface apparatus for exhausting anesthetic gases from the patient circle without exposing the patient to direct vacuum application.
It is a further object that the safety interface so provided affords an access to ambient air whereby positive pressure build up in the line, such as may be caused during inadvertent exhaust line occlusion, will not be passed on to the patient.
Another common application in anesthesia administration in the use of reservoir bags in the patient circle which provides a reservoir, and also allows the anesthesiologist to provide predetermined back pressure to the patient by squeezing the bag (i.e., commonly known as "bagging" the patient). It is a further object of the present invention to provide a storage reservoir capacity whereby ventilation exhausts created by bagging may be relieved without causing excessive pressure in the system due to pressure drop in the vacuum exhaust circuit.